This invention relates to an apparatus for supplying a liquid heated to a predetermined temperature. In particular, the invention relates to apparatus for intermittently supplying a dental treating solution to the oral cavity of a patient with the solution being heated to about the normal body temperature of the patient, and to a method of treating employing such apparatus.
A common method for removing carious lesions in teeth is through the use of power operated tools in conjunction with hand manipulated tools. Thus, complete removal of carious material by the dentist requires the use of rotary cutting instruments as well as hand instruments. Such dental procedures impart a high degree of apprehension and fear to many dental patients, particularly children. Other dental patients have problems and/or reactions with local anesthetic injection which are oftentimes given in those instances where the carious lesions are fairly extensive and deep.
Within the past decade, methods have been developed which utilize certain chemical solutions to soften and remove dental caries. Such methods substantially reduce and even eliminate the need for mechanical removal of the carious lesion by the use of drills and burrs. Suitable solutions can be prepared by forming an admixture containing (a) at least one aminoalkanoic acid containing from 1 to about 18 carbon atoms, e.g., DL-2-aminobutryic acid, glycine, etc., (b) an alkali metal hydroxide, e.g., sodium hydroxide, (c) an alkali metal halide, e.g., sodium chloride, and (d) an alkali metal hypochlorite, e.g., sodium hypochlorite, in deionized water and preferably maintained at a pH of from about 9 to about 12. The active ingredient is believed to be N-chlorinated aminoalkanoic acid(s) and/or the alkali metal salt(s) thereof. A preferred formulation is (a) DL-2-aminobutyric acid and/or glycine, (b) sodium hydroxide, (c) sodium chloride and (d) sodium hypochlorite. The molar ratios of components (a), (b) and (c) can vary advantageously are about 1:1:1 with the molar ratio of component (a) relative to component (d) exceeding 1, e.g., about 5 to 10, in one liter of deionized water. The active ingredient presumably reacts with the decalcified, partially degraded collagen of the carious lesion resulting in a softening of the carious material. For information on this subject, reference is made to U.S. Pat. Nos. 3,886,266; 3,932,605; 3,991,107; 4,012,842; and 3,776,825, the subject matter of which is incorporated herein by reference. The aforesaid caries removal solution has a relatively short half life and should be prepared just prior to use.
A delivery system for administering the caries removal solution to the carious lesion is disclosed in U.S. Pat. Nos. 3,776,825 and 3,943,628 and can consist of a reservoir for the solution, a pump having an inlet connected to the reservoir and a handpiece with a uniquely designed applicator tip connected to the outlet side of the pump. The solution is delivered in a fine pulsing stream through the handpiece to the carious site where it softens the decayed material. The dentist can then remove the softened carious material by light abrasion with the applicator tip while flushing with the solution.
Prior attempts to employ a caries removal device or system which comprises solely an applicator, a source or reservoir of the chemical solution and pump means connected between the applicator and the chemical solution source for periodically delivering the chemical solution under pressure to the applicator have not proven particularly successful.
Desirably, the temperature of the caries removal solution at the time of application to the carious lesion should be maintained within a range that affords maximum comfort to the dental patient, e.g., from about 90.degree. F. to about 105.degree. F., which covers the range of normal body temperature of the patient. A temperature significant beyond this range can cause discomfort and may traumatize the patient.
The chemical solution is desirably applied to the carious lesion as a soothing, pulsating stream through a tube connected to the applicator tip at an optimum flow rate of about 35.+-.5 ml/minute. The pulsation frequency of the stream is desirably maintained in the range of about 1000 to 1600 cycles/minute while its pressure is advantageously varied from about 10 to about 15 psi (per pulsation cycle). The flow rate, pulsation rate and pressure of the stream should be selected so as to balance facility of application of the stream to the caries site with due regard for the patient's comfort.
In order to achieve these objectives, the chemical solution must be heated from an ambient state when placed in the reservoir to approximately 98.6.degree. F., or normal body temperature. Thus, it has been suggested in U.S. Pat. Nos. 3,863,628 and 4,012,842 to employ a heater as a part of the pump to bring the chemical solution to body temperature as it is pumped to the applicator. The heater includes a heating element embedded in a conductive block forming one side wall of the pump chamber. The block is disposed opposite to, and spaced from, a flexible diaphragm which is reciprocated so that chemical solution from a reservoir is received in the chamber between the diaphragm and heater block and forced by the diaphragm out of the chamber to a hand-held applicator during reciprocation of the diaphragm by a cam mechanism connected to a drive motor. This arrangement proves impractical in that the diaphragm cannot withstand the required frequency of operation cycle and fails after a relatively brief period of service
Further, while the dwell time of the cam mechanism between the diaphragm and drive motor can be adjusted to increase or decrease the relaxation, or inactive, period of the pump to cause a pulsating drive of the chemical solution, there are no means to regulate the flow rate or pressure of application of the chemical solution, which, if too high, can cause harm to the patient by tearing of gum tissue adjacent the treated teeth.
Thus, the need for an improved chemical solution delivery system for applying the solution to a tooth with a carious lesion in a pressure and flow-controlled, properly heated state, is desirable.
It has long been known that reciprocating, piston-type pumps can be used to deliver a pulsating stream or jet of water to teeth for oral hygiene such as cleansing, massaging and stimulating gum tissue. Examples of such pump constructions are shown in U.S. Pat. Nos. 3,227,158 and 3,420,228, the former illustrating the pump forming the basis of the well-known WATER-PIK system. Such pumps do not exhibit the objectionable wear characteristics typical of a bellows or flexed diaphragm-type active pump element and through the introduction of suitable valving adjacent the inlet and outlet of the pump chamber, flow and pressure control of the pumped fluid may be obtained.
The disadvantages associated with known types of heated liquid delivery systems are not confined to the aforementioned diaphragm-type pumping mechanisms. The heater devices which have been incorporated into these system are inadequate to the task for reasons which are inherent in their design.
In a known type of heater device, a liquid to be heated is circulated about, or otherwise brought into direct contact with, an electrically powered insulated heating element with heat being transferred from the heating element to the liquid. The heater device is associated with suitable control means for heating the liquid at r within a few degrees of a predetermined temperature. The device operates well when there is a sufficient flow of liquid past the heating element to continuously carry away heat therefrom. However, when the delivery of electrical power to the heating element is temporarily interrupted, e.g., when the flow of liquid is discontinued, residual heat from the heating element continues to transfer to the liquid in the vicinity of the heating element causing the liquid to overheat. In fact, overheating can occur to such an extent that the liquid in proximity to the heating element begins to boil. Such a heater device is therefore entirely unacceptable for heating liquids to be contacted with, or introduced into, the body. Such a device poses the additional disadvantage that in the case of a corrosive liquid, there is a danger that the liquid will eventually penetrate the casing of the heating element thereby coming into electrical contact with the liquid. The hazard of an accidental electrocution in such circumstances is in itself sufficient reason to preclude the use of such a heater device in apparatus intended to supply a heated body-treating liquid.